Jef
 
We only measured pronated feet in that initial study. But we can test what you are saying - I think you are probably right. We will be doing more work on it this year.
 
CP

________________________________

From: A group for the academic discussion of current issues in podiatry on behalf of Jeff Root
Sent: Sun 1/02/2004 2:56 AM
To: [log in to unmask]
Subject: Re: Orthotics and the force required to dorsiflex the hallux


Craig,
 
Did you say that all feet seem to require less force to dorsiflex the hallux while wearing orthoses.  Is my recollection correct?  If so, then according the Eric and Kevin's theory would not feet with excessive STJ supination that are less supinated at the STJ during relaxed stance while wearing orthoses require more force to dorsiflex the hallux due to a medial shift in the STJ axis?  If this theory is potentially valid, then you should find that all feet in which the RCSP is less supinated or more pronated while wearing orthoses as compared to no orthoses should actually require more force to dorsiflex the hallux.
 
Dorsiflexing the hallux is a pure sagittal plane action.  Therefore I would expect the initial retrograde compensation to be an opposite sagittal plane moment of the 1st met or first ray (ie plantarflexion moment of the 1st met or 1st ray).  Secondarily, if the MTJ were maximally pronated from ground reaction, then the MTJ would undergo a sagittal plane plantarflexion moment as well.  The MTJ is the joint where we should see conversion of sagittal plane motion to triplane motion (MTJ supination) since the compound axes of the MTJ tend to promote triplane motion.  
 
When you dorsiflex the hallux the primary motions observed are sagittal plane changes.  The hallux dorsiflexes, the 1st ray plantarflexes due to elevation of the base of the 1st ray.  If there is no observable frontal plane motion of the posterior aspect of the calcaneus, then the compensation is largely sagittal plane in nature or may not be influencing the STJ due to compensation at other joints.  In other words, the forces created by dorsiflexion of the hallux are compensated somewhere other than the STJ.   
 
Respectfully,
 
Jeff Root
 
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